The present invention relates to electrical keyboards and, in particular, to a lighted, membrane switch type keyboard operative to provide the operator with the sensation of full travel keys, although manufacturable with a minimum number of pieces.
Electrical switch containing keyboards, such as used in typewriters, calculators, data entry terminals, etc., generally employ relatively large keys with relatively large on-center spacings. These keys are typically rather complex in construction and operate, not only to make switch contact, but to provide an operator with a tactile sensation or feedback, whereby the operator is assured of having made switch contact. Previously, switches have employed a variety of structures ranging from spring loaded assemblies to dome type switch elements to provide this tactile feedback signal. The present invention, however, seeks to provide this tactile feedback in a less complex assembly. In particular, it is an object of the present invention to achieve tactile feedback with a membrane type switch assembly, while providing for back lighted keys.
Prior art switches containing one or more of the features of the present switch can be found upon referring to U.S. Pat. Nos. 3,780,237; 4,304,973; 4,362,911; and 4,370,532. Disclosed in these patents are various switch assemblies that include foam separated membrane switch layers, flange containing switch plungers mountable relative to a key-cap, foam spacers mounted beneath the key-caps and intermediate a membrane switch and a multi-sectioned lighted push button key. Many of the features of the present switch are, therefore, singularly included in these switches. The present invention, however, seeks to combine all of these features in a single, low complexity keyboard of novel construction.
In particular, the keyboard of the present invention utilizes a side-lighted transparent support plane having a plurality of integrally formed light-pipes extending therefrom. Mounted about the light-pipes and overlying the support plane is a foam over-travel pad and above which are mounted one or more patterned membrane switch layers, separated from one another via low density foam spacers. Mounted relative to the patterned switch layers and light pipes are a plurality of key-caps that are slidably operable along the light pipes so as to make switch contact and provide the operator with a tacticle feedback. The caps are contained to the light pipes via flanges and may contain a molded projection interactive with a mating projection on the light pipe for providing the operator with a further "click" like feeling.
The above-mentioned objects, advantages and distinctions of the present keyboard, its construction, as well as various other objects and advantages will become more apparent upon directing attention to the following description thereof with respect to the following drawings. Before referring thereto, though, it is to be recognized that the present description is made with respect to the presently preferred embodiment only and, therefore, various modifications may be made thereto without departing from the spirit and scope hereof.